Hyperglycemia or abnormally high glucose levels, occurs when the body has too little insulin, or when the body cannot use insulin properly. It occurs in people with diabetes and if left untreated, this condition can lead to coma or death.
Patients with diabetes are therefore required to regularly monitor their blood glucose levels, so as to manage food intake and the dosage and timing of insulin injection.
There are presently various methods adopted to allow patients to monitor their blood glucose levels, and are broadly grouped into two broad categories—invasive and non-invasive.
Invasive Monitoring
Invasive blood monitoring is by analysing the blood of a patient. This is usually done by obtaining a drop of blood, usually from the finger. This blood is then placed on a strip containing reagents that react with glucose to form a chromophor. This is subsequently read by a reflectance calorimeter within an analyser, to determine the level of glucose present in the blood.
The blood is obtained by the use of lancets, laser sensors (known commercially as Lasettes), or silicon micro-needles, just to name a few.
However, as patients need to check their blood glucose levels usually several times a day, invasive monitoring methods are not ideal. More importantly, the used needles or lancets may cause contamination, and should be treated as bio-hazards. Used needles or lancets must be disposed of properly.
Non-invasive Monitoring
Non-invasive monitoring techniques and methods are preferred, as these methods do not cause physical injury, nor do they contribute to the stress and discomfort to a patient.
The current non-invasive monitors include the following:                a. Interstitial fluid monitors that are depressed against the skin to obtain a glucose reading. However, glucose levels in interstitial fluid may lag a few minutes behind those of capillary blood. Therefore, the readings obtained are not real time information, which may be crucial.        b. Glucose sensing lenses, which are used together with a near infrared energy source. This energy illuminates the eye, and is passed through the aqueous human in the anterior chamber of the eye and then reflected from the iris. The reflected energy is collected for analysis, and is an indication of the glucose concentration in the patient's blood. However, this method though technically non-invasive, can hardly be said to be non-obtrusive.        c. Optical absorption technique, in which an incident infrared light source is delivered through an optical fibre to a probe for measurement. On the same probe, there is corresponding optical fibre to deliver the diffused light from the point of measurement to a photo diode for subsequent data processing.        
Of these 3 approaches, the optical absorption technique for quantification of glucose using infrared light source has demonstrated to be a very promising approach for non-invasive blood glucose sensing.
However, a huge drawback of this technique is that when the probe comes in contact with the body surface, a major problem arises from contact pressure. The contact pressure however small will have an influence on the body tissue compression (immediately beneath the skin/nail) and hence will affect the blood flow. For instance, a large contact pressure of the probe can result in occluding the flow on tissue (immediately beneath the skin) and blood flow, leading to tissue blanching.
In the optical absorption technique for non-invasive blood glucose sensing, an incident infrared light is directed through the skin/nail and is absorbed by blood (glucose) that is immediately beneath. Therefore, if the blood flow beneath the skin/nail varies due to varying contact pressure, then a fluctuating signal output is inevitable. The signal output is received by an infrared sensor, (or photodiode) which is very sensitive. A small variation of contact pressure is known to create a large fluctuation in the signal output.
In non-invasive blood glucose sensing application, the probe is expected to be applied repeatedly for measurement at the convenience of the user. Hence variation of contact pressure of the probe in repeated measurements is known to cause large fluctuation in signal output leading to high uncertainty or inaccuracy of the actual blood glucose reading of a patient.
It is an object of the present invention to overcome or at least ameliorate one or more of the above problems in the prior art.
Discussion of any one of the prior art mentioned above is not to be taken as an admission of the state of common general knowledge of the skilled addressee.